Does A Webasto Diesel Heater Affect My Mpg?

[Teesix]

Odd question but, if I leave the webasto heater running all night, does that affect the average mpg on the MFD?

Presumably the fuel used by the heater would be considered fuel used by the engine, as far as the MFD is concerned. Assuming it calculates mpg on fuel used/remaining in the tank that is.

Is this the case?

 

[Loz]

Correct

 

[Teesix]

Thank you Loz

I'm trying the heater out in anger tomorrow night so will be interesting how much it affects the MPG.

 

[Daffy]

I don’t think it does, I can’t speak about VW but truck manufacturers (I worked for one) have a flow meter on the engine that monitors the volume of fuel being consumed by the engine and the calculation is made by the system based on distance travelled.

Therefore any fuel taken from the tank directly such as the heater won’t affect the display reading, it will however affect any calculations you make based on fuel put in the tank.

Thinking about it, if it was simply about the level of the tank then any short journey mpg figure or instantaneous figures would be very unreliable.

I could be wrong...

 

[Tourershine]

A mate of mine has fitted his diesel heater a couple of months ago.
This chap is as tight as they come, and he knows to the penny exactly what things are costing him, and moans for weeks if he's paying something more than he expected. (good mate though)
He's been running his heater during the cold snaps first thing in the morning, so his cab is warm when he gets in for work. He's also been away several times and used the heater.

I've not heard him moan once about the cost of running the heater, and believe me, it's all he'd talk about if it was costing him more than he was quoted by the manufacture.


On the basis that my WhatsApp isn't full of 'moan' messages, they must use next to no noticeable diesel

 

[Loz]

Think of it like this.
You fill the tank with fuel and run the heater until half the tank is used and then drive on the remaining half.
You then brim the tank and do your mpg calculations and you have halved your usual mpg. So yes it affects mpg.

However, in reality the heater uses a very small amount for the time its used compared to driving so you are more likely to cover the fuel used by the heater by your driving conditions. Just one overtaking squirt will use more extra fuel that a nights worth of gentle heating. Therefore over a tank it is no noticeable drop in mpg.

 

[rod_vw]

No the engine still uses the same amount of fuel but if you think about your question that is bound to be the case.

However it does use fuel direct from the tank but I would doubt that even if you measure exact fill brim to brim you would ever be able to calculate the usage. I have used Eberspachers for years and also been fastidious in recording all fuel put into the tank but never seen a noticeable difference even when we have used the heater over night for a number of nights.

@Loz I believe that the MFD calculates its MPG figure from the injection quantities (opening timing of the injectors) and miles covered all worked out by the ECU (or Instrument cluster), clever computer algorithms!

Rod

 

[Salty Spuds]

Think of it like this.
You fill the tank with fuel and run the heater until half the tank is used and then drive on the remaining half.
You then brim the tank and do your mpg calculations and you have halved your usual mpg. So yes it affects mpg.

However, in reality the heater uses a very small amount for the time its used compared to driving so you are more likely to cover the fuel used by the heater by your driving conditions. Just one overtaking squirt will use more extra fuel that a nights worth of gentle heating. Therefore over a tank it is no noticeable drop in mpg.

But it doesn’t affect the MPG on the MFD. the MPG/MFD is a calculated figure based on the amount of diesel being fed to the engine by the ECU & distance travelled. The fuel for the Webasto doesn’t go through the metering system. It will obviously affect the “real” MPG that you calculate with a brim to brim tank fill. But not the readout on the MFD.

 

[Teesix]

Well I'm just back and can confirm what Daffy, Rod and Salty have said - there's no effect to the MPG on the MFD.

Obviously the brim-to-brim figures would be affected but I'm glad the MFD doesn't display it. I was having visions of when I come to sell the van only for the prospective buyer to ask why I was only getting 10 to the gallon out of it!

Have to say, I'm pretty pleased with the Webasto. The van has been nothing but really toasty for the last few days. It even heated the awning.

 

[Loz]

Yes, I was thinking brim to brim as I don't trust the MFD. (should have read your first post properly)

 

[Salty Spuds]

Well I'm just back and can confirm what Daffy, Rod and Salty have said - there's no effect to the MPG on the MFD.

Obviously the brim-to-brim figures would be affected but I'm glad the MFD doesn't display it. I was having visions of when I come to sell the van only for the prospective buyer to ask why I was only getting 10 to the gallon out of it!

Have to say, I'm pretty pleased with the Webasto. The van has been nothing but really toasty for the last few days. It even heated the awning.

You can reset the MFD mpg at anytime. Just reset it, & drive carefully for 50 miles & both readouts 1&2 will be reading high mpg.

 

[Scuba Moir]

A mate of mine has fitted his diesel heater a couple of months ago.
This chap is as tight as they come, and he knows to the penny exactly what things are costing him, and moans for weeks if he's paying something more than he expected. (good mate though)
He's been running his heater during the cold snaps first thing in the morning, so his cab is warm when he gets in for work. He's also been away several times and used the heater.

I've not heard him moan once about the cost of running the heater, and believe me, it's all he'd talk about if it was costing him more than he was quoted by the manufacture.


On the basis that my WhatsApp isn't full of 'moan' messages, they must use next to no noticeable diesel

Lol, I know its a old inquiry, but is his name Phil, I got one exactly the same, whengoing on a trip, down to the last penny.

 

[Linoleum Bonypart]

Don't they use something like 0.5l per hour??

 

[Scuba Moir]

Don't they use something like 0.5l per hour??

Sorry for the misunderstanding, I ment I have one the same as in a mate, being tight as a arse. But on a good note, when my van is built, thats what I'm also having fitted. I have been told they dont use much that you would notice..

 

[Linoleum Bonypart]

Sorry for the misunderstanding, I ment I have one the same as in a mate, being tight as a arse. But on a good note, when my van is built, thats what I'm also having fitted. I have been told they dont use much that you would notice..

Just ordered a planar heater... Quality heater without paying for the webasto name

 

[Dannyb6467]

Just ordered a planar heater... Quality heater without paying for the webasto name

Keep us informed how this goes please pal, looking to book mine in for fitting January.

 

[DXX]

I’ve got a Wallas hob / heater, it uses 0.09L - 0.18L per hour, that’s a 1800W heater at max capacity.
Diesel heater fuel consumption is very low.